Rocker arms transmit motion from a rotating cam shaft to a stem of a poppet valve to open and close the valve. Almost universally, the valve is spring-biased shut and the cam via the rocker arm controls the opening and closing of the valve. One type of rocker arm is the finger follower rocker arm.
In recent times, rocker arms have been made to selectively deactivate to allow enhanced control of vehicle engines in regard to emissions and fuel economy. In one such rocker arm assembly, the rocker arm 23 (FIG. 9) has an outer body 25 that engages the valve stem (not shown) and an inner lost motion arm 27 pivotally mounted on and within the outer body for movement relative to the outer body. The lost motion arm 27 is spring-biased upward against an overhead engine cam lobe (not shown) to be pivoted by the same. A latching mechanism with an extendable plunger 29 is positioned within the outer body 25. The plunger 29 is normally in a position to limit movement of the lost motion arm 27 relative to the outer body 25 so that the cam lobe can pivot the outer body 25 and lost motion arm 27 together as an integral unit to activate the valve stem. Withdrawal of the latch mechanism plunger 29 allows the lost motion arm 27 to freewheel in a lost motion manner without causing any partial or full movement of the outer body 25 and valve stem.
Currently, such selectively deactivation rocker arm assemblies are valve lift limited due to a condition termed "super submarining" (hereinafter referred to as submarining) wherein the rocker arm assembly is permanently locked in a valve deactivated condition. Submarining occurs when the lost motion arm is inadvertently held underneath an extended plunger 29. Submarining causes the cylinder serviced by the submarining rocker arm 23 to be permanently disabled. When the submarining occurs, major disassembly of the vehicle engine is required to alleviate the situation. Prior to the present invention, the valve lift and engine speed have been compromised by limiting them to such levels so as to prevent the lost motion control arm 27 from passing below the plunger 29. It is desirable to provide a rocker arm assembly which is self-alleviating from any potential submarining conditions.